The present invention relates to a coupling. More particularly this invention concerns a resilient coupling for transmitting torque between a pair of generally coaxial rotatable elements.
A standard shaft coupling such as described in British patent document 2,078,907 of Walter or German patent documents 678,017, 3,109,388 of Walter, 3,616,232 of Bohm, 4,215,539 of Kirschey, or 91 000 835 assigned to KTR has a pair of generally coaxial elements one of which is driven and the other of which is connected to a load, and at least one elastomeric body having end faces adhered to the elements so as to transmit torque therebetween while still permitting the rotation axes of the elements to be slightly misaligned. The elastomeric body also serves to smooth out momentary increases or decreases in rotation speed of either the input or output element. Such couplings are typically used to drive a generator or a watercraft propeller from a gasoline or diesel engine.
In the arrangement of above-cited British patent document 2,078,907 of Walter there are two such elastomeric bodies formed as rings each having an outer face lying on a plane perpendicular to the coupling axis and bonded to a respective one of a pair of plates that are rigidly connected together and a frustoconical inner face bonded to outer faces of a multipart element connected via further elastomeric bodies to the other element of the coupling. Such a construction is quite complex and tends to overheat when compensating for substantial misalignment or for irregular input or output speed.
It is therefore an object of the present invention to provide an improved shaft coupling.
Another object is the provision of such an improved shaft coupling which overcomes the above-given disadvantages, that is which is of relatively simple construction, but which can be sure to run cool even when compensating for considerable misalignment or varying input or output speeds.
A coupling has according to the invention a pair of elastomeric rings centered on a common axis and having generally frustoconical inner faces confronting each other and generally planar outer faces extending generally perpendicular to the axis and directed oppositely away from each other. Respective generally planar, rigid, and annular outer plates centered on the axis are bonded to the outer faces. A metallic center body having frustoconical outer faces bonded to the ring inner faces is formed with a plurality of radially throughgoing center passages.
Thus this coupling is cooled by air flow through these center passages, at the very core of the chuck where heat buildup is most likely. The cooling is automatic in that as the chuck rotates air in the passages will be driven centrifugally outward, drawing in more cooling air to produce a cooling effect that is roughly proportional to speed, exactly as needed. Furthermore the shape of the elastomeric bodies makes manufacture of the coupling particularly easy, specially when done with laser- or plasma-cutting systems. The center body is cast of a light-metal alloy of high conductivity, aluminum being particularly suitable. The provision of the cooling passages in the cast center body in no way weakens the coupling while allowing the elastomeric bodies to be made solid, that is with no cooling passages.
The center-body outer faces diverge radially inward and extend substantially symmetrically to a center plane bisecting the center body and perpendicular to the axis. The center body is a pair of frustoconical plates having confronting faces formed with radially extending ribs defining the center passages and bearing axially on each other. These plates can be unitary or separate. The elastomeric rings can be of one piece or, for transmitting large torque, formed of several segments. Even the outer plates can be made of separate segments.
In accordance with the invention a one-piece stabilizing ring between the elastomeric bodies bears radially outward on the ribs of the outer plates. A plurality of bolts engage through the center-body plates at the ribs with the stabilizing ring. The stabilizing ring defines with each of the center-body plates an annular gap communicating with the center passages. Furthermore the ribs form a radially inwardly open groove complementarily receiving the stabilizing ring.
Each ring inner face can have an inner portion extending in a plane perpendicular to the axis. This shape is used in a coupling intended for transmitting considerable torque.
A drive hub is rotatable about the axis adjacent one of the outer plates and a flexible membrane plate has an inner periphery connected to the drive hub and an outer periphery fixed to the one outer plate. Such a membrane plate is useful for compensating out small axial and radial misalignments of input and output members connected to the coupling. The membrane plate is formed with axially throughgoing holes communicating with the center passages.
A flywheel is rotatable about the axis adjacent one of the outer plates. A spacer plate sandwiched between the flywheel and the one outer plate forms a plurality of radially through-going outer passages. This spacer plate has an annularly continuous inner portion spaced radially inward of an inner periphery of the one outer plate and a plurality of notch-defining arms sandwiched extending radially outward from the inner portion between the one outer plate and the flywheel. The one outer plate is formed with cutouts aligned between the notch-defining arms and forming outermost portions of the outer passages.
In a system intended for large torque transmission, a drive member is connected to one of the outer plates, a driven member to the center body, and a sleeve is bolted between and fixed to both of the outer plates.